The following exhaust pipe structure for motorcycle is known. In the exhaust pipe structure, exhaust pipes extend from respective cylinders of a multicylinder engine, and a single silencer is placed at downstream ends of these exhaust pipes. The silencer is divided into expansion paths which are independent of one another and are equal in number to the number of the cylinders in the multicylinder engine. (For example, see Japanese Patent No. 3196953, FIGS. 6 and 7).
In FIG. 6 of Japanese Patent No. 3196953, a muffler (hereinafter, the muffler is referred to as the “silencer,” of a motorcycle has three independent expansion paths led from the respective cylinders. By partitions provided to radially extend in a tubular member, each of these three expansion paths is divided into three expansion chambers: a first expansion chamber, a second expansion chamber, and a third expansion chamber. The first expansion chamber and the second expansion chamber communicate with each other by a pipe, and the second expansion chamber and the third expansion chamber communicate with each other by a pipe.
In FIG. 7 of Japanese Patent No. 3196953, the silencer is divided into the three independent expansion paths by partition plates extending axially in the tubular member. The exhaust pipes extending from the cylinders are led to these three expansion paths, respectively. The three expansion paths provided in the tubular member have almost the same capacity. Note that the capacity is a volume that a container can hold.